The Company offers payment terms of more than one year for qualified customers and transactions in some circumstances. At times, revenue recognition occurs before billing, resulting in an unbilled receivable, which represents a contract asset. The contract asset is a component of accounts receivable and other assets for the current and non-current portions, respectively.

Customer advances represent deposits from customers for shipments of systems. Deferred revenue balances represent active and non-active warranties and services, which are recognized based on contract terms.

	September 30, 2019		June 30, 2019
(Dollars in thousands)	Amount		Amount
Contract Assets:
Unbilled accounts receivable – current (1)	$	7,643	$	5,260
Interest receivable – current (2)		584		361
Long-term accounts receivable (2)		3,081		4,116
Interest receivable – non-current (2)		1,079		1,255
Contract Liabilities:
Customer advances		18,413		20,395
Deferred revenue – current		79,596		78,332
Deferred revenue – non-current		26,273		26,639

(1)

Included in accounts receivable on consolidated balance sheets

(2)

Included in prepaid expenses and other current assets on consolidated balance sheets

(3)

Included in other assets on consolidated balance sheets

During the quarter ended September 30, 2019, contract assets changed primarily due to the timing of billings occurring after revenues were recognized and payment terms exceeding 12 months. Contract liabilities changed due to timing of system sales for which the warranty has not yet started and was deferred and due to changes in transaction price.

	Three Months Ended
(Dollars in thousands)	September 30, 2019			June 30, 2019
Balance at beginning of period	$	104,971		$	102,124
New billings		90,475			120,263
Recognition of deferred revenue from opening balance		(11,191	)		(22,619	)
Recognition of new additions		(78,386	)		(94,797	)
Balance at end of period	$	105,869		$	104,971

Remaining performance obligations represent deferred revenue from open contracts for which performance has already started and the transaction price from executed and non-cancellable contracts for which performance has not yet started. Service contracts in general are considered month-to-month contracts, and therefore, the Company has elected the practical expedients to not disclose the value of unsatisfied performance obligations for contracts with an original expected duration of one year or less.

As of September 30, 2019, total remaining performance obligations amounted to $881.1 million. Of this total amount, $82.3 million related to long-term warranty and service, which is expected to be recognized over the remaining warranty period for systems that have been delivered. For systems that have been delivered but not yet installed, management estimates the timing of installation since warranty starts upon installation.

The following table represents the Company's remaining performance obligations related to long-term warranty and service as of September 30, 2019 and the estimated revenue expected to be recognized:

	Fiscal years of revenue recognition
(Dollars in thousands)	2020		2021		2022		Thereafter
Long-term warranty and service	$	28,619	$	26,649	$	14,714	$	12,332

For the remaining $798.8 million of performance obligations, the Company estimates 21% to 30% will be recognized in the next 12 months, and the remaining 70% to 79% will be recognized in the 30 months thereafter. The Company’s historical experience indicates that some of its customers will cancel or renegotiate contracts as economic conditions change or when product offerings change during the long sales cycle. Based on historical cancellations, about 24% of the Company’s contracts may never result in revenue due to cancellation.

The time bands reflect management’s best estimate of when the Company will transfer control to the customer and may change based on timing of shipment, readiness of customers’ facilities for installation, installation requirements, and availability of products.

The Company capitalizes and amortizes the incremental costs of obtaining a contract, primarily related to certain bonuses and sales commissions. The capitalized bonuses and sales commissions are amortized over a period of five years commencing upon the initial transfer of control of the system to the customer following the pattern of transfer of control of the performance obligations to the customer.

The balance of capitalized costs to obtain a contract was $8.7 million and $6.2 million as of September 30, 2019 and 2018, respectively. The Company has classified the capitalized costs to obtain a contract as a component of prepaid expenses and other current assets and other assets with respect to the current and non-current portions of capitalized costs, respectively, on the consolidated balance sheets. The Company incurred impairment losses of $0.1 million and $0 in the three-month periods ended September 30, 2019 and 2018, respectively. The Company recognized $0.5 million and $0.9 million in expense related to the amortization of the capitalized contract costs during the three-month periods ended September 30, 2019 and 2018, respectively .